The invention relates to a lamp comprising a discharge vessel provided with a wall of densely sintered translucent aluminum oxide formed for the major part from crystals having a size of at most 60 .mu.m.
Such a lamp is known from U.S. Pat. No. 4,214,666 in the form of a high-pressure discharge lamp. When used as material for the discharge vessel, the densely sintered translucent aluminum oxide is exposed to corrosive action of partly ionized filling constituents at temperatures up to approximately 1500 K. Although in practice lamps are realized having a life of a few thousands of operating hours, it has been found that in a number of cases the wall material is attacked by filling constituents during the life of the lamp. This results inter alia in filling constituents being extracted from the discharge and hence in the properties of the lamp being changed; for example, the specific light output is reduced, the arc voltage increases and there is a risk of the discharge vessel becoming leaky. A discharge vessel that has become leaky has reached the end of its life.
A discharge vessel provided with a wall of aluminum oxide is known from British Pat. No. 1034122, in which the inner surface of the wall is formed from a single crystal. Although satisfactory gas-tightness of the wall of the discharge vessel is thus obtained, it has been found that with such a stratified structure of the lamp ruptures are inevitably formed as the stratified parts fail under practical operating conditions of the discharge lamp. This leads to the end of the life of the lamp.